In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté for about 3-4 minutes until translucent. Add the minced garlic and sliced mushrooms, cooking for another 5 minutes until the mushrooms are tender.

Increase the heat to medium-high and add the ground beef to the skillet. Cook until browned, breaking it apart with a spatula, about 5-7 minutes. Drain excess fat if necessary.

Stir in the Worcestershire sauce, Dijon mustard, and beef broth. Bring to a simmer and let it cook for about 5 minutes.

In a small bowl, mix the flour with a few tablespoons of the sour cream to create a smooth paste. Gradually stir this mixture back into the skillet, followed by the remaining sour cream. Reduce the heat to low and cook for an additional 3-4 minutes until the sauce thickens. Season with salt and pepper to taste.

Meanwhile, cook the egg noodles according to package instructions. Drain and set aside.

Serve the beef stroganoff over the cooked egg noodles. Garnish with chopped parsley if desired.